We are kind of extinct specie
Still there is some community left.
70 players total on 19 servers, - what my IL2SFB connector shows right now - screenshot below. Probably half of them are interested in turn and burn play only.
There were 9 players on Orel War yesterday around 07-10PM GMT. Which was probably the highest number I saw in the last month. And sometimes I encounter only AI there.

May be more people could join to coop if invitation is published elsewhere. SAS forum?

Coops indeed need players that are even remotely coop oriented. A coop mission must provide something that a server cannot. If you want to get players, include some exotic or rarely seen maps and especially planes.

Speaking of which, Vinni Puh server has at least two early N1K1 variants on the plane list! Finally! On the Solomons map! It's the best plane in the game! Everything, and I mean everything looks, feels and works right with it. It's like Zero and Fw 190 had a baby! Forget the N1K2 and other nonsense planes, pick a N1K1!